How to fix Normal Map Artifacts (Humanoid)
Thanks to @mobin for prompting me regarding my cage, I did some further research and found out the proper way to do a cage.
My steps to resolve artifactings:

Duplicate lowpoly model, and name as Cage
Select all faces of Cage, alt s, to scale up the faces in normal directions
Toggle on mirror selection mode
Compare Cage to High Poly model, and push out all faces to completely surround the High Poly. i.e. Cage should be slightly bigger than the High Poly
Ensure there are no overlapping faces, i.e. tight areas like fingers and groin can be problematic, and require quite abit of manual adjustments
Bake for a perfect normal map